diff --git a/libcacard/vscard_common.h b/libcacard/vscard_common.h
new file mode 100644
index 0000000..5cb6eb5
--- /dev/null
+++ b/libcacard/vscard_common.h
@@ -0,0 +1,167 @@
+/* Virtual Smart Card protocol definition
+ *
+ * This protocol is between a host using virtual smart card readers,
+ * and a client providing the smart cards, perhaps by emulating them or by
+ * access to real cards.
+ *
+ * Definitions for this protocol:
+ *  Host   - user of the card
+ *  Client - owner of the card
+ *
+ * The current implementation passes the raw APDU's from 7816 and additionally
+ * contains messages to setup and teardown readers, handle insertion and
+ * removal of cards, negotiate the protocol via capabilities and provide
+ * for error responses.
+ *
+ * Copyright (c) 2011 Red Hat.
+ *
+ * This code is licensed under the LGPL.
+ */
+
+#ifndef VSCARD_COMMON_H
+#define VSCARD_COMMON_H
+
+#include <stdint.h>
+
+#define VERSION_MAJOR_BITS 11
+#define VERSION_MIDDLE_BITS 11
+#define VERSION_MINOR_BITS 10
+
+#define MAKE_VERSION(major, middle, minor) \
+     (  (major  << (VERSION_MINOR_BITS + VERSION_MIDDLE_BITS)) \
+      | (middle <<  VERSION_MINOR_BITS) \
+      | (minor)  )
+
+/** IMPORTANT NOTE on VERSION
+ *
+ * The version below MUST be changed whenever a change in this file is made.
+ *
+ * The last digit, the minor, is for bug fix changes only.
+ *
+ * The middle digit is for backward / forward compatible changes, updates
+ * to the existing messages, addition of fields.
+ *
+ * The major digit is for a breaking change of protocol, presumably
+ * something that cannot be accomodated with the existing protocol.
+ */
+
+#define VSCARD_VERSION MAKE_VERSION(0,0,2)
+
+typedef enum VSCMsgType {
+    VSC_Init = 1,
+    VSC_Error,
+    VSC_ReaderAdd,
+    VSC_ReaderRemove,
+    VSC_ATR,
+    VSC_CardRemove,
+    VSC_APDU,
+    VSC_Flush,
+    VSC_FlushComplete
+} VSCMsgType;
+
+typedef enum VSCErrorCode {
+    VSC_SUCCESS=0,
+    VSC_GENERAL_ERROR=1,
+    VSC_CANNOT_ADD_MORE_READERS,
+    VSC_CARD_ALREAY_INSERTED,
+} VSCErrorCode;
+
+#define VSCARD_UNDEFINED_READER_ID  0xffffffff
+#define VSCARD_MINIMAL_READER_ID    0
+
+#define VSCARD_MAGIC (*(uint32_t*)"VSCD")
+
+/* Header
+ * Each message starts with the header.
+ * type - message type
+ * reader_id - used by messages that are reader specific
+ * length - length of payload (not including header, i.e. zero for
+ *  messages containing empty payloads)
+ */
+typedef struct VSCMsgHeader {
+    uint32_t   type;
+    uint32_t   reader_id;
+    uint32_t   length;
+    uint8_t    data[0];
+} VSCMsgHeader;
+
+/* VSCMsgInit               Client <-> Host
+ * Client sends it on connection, with its own capabilities.
+ * Host replies with VSCMsgInit filling in its capabilities.
+ *
+ * It is not meant to be used for negotiation, i.e. sending more then
+ * once from any side, but could be used for that in the future.
+ * */
+typedef struct VSCMsgInit {
+    uint32_t   magic;
+    uint32_t   version;
+    uint32_t   capabilities[1]; /* receiver must check length,
+                                   array may grow in the future*/
+} VSCMsgInit;
+
+/* VSCMsgError              Client <-> Host
+ * This message is a response to any of:
+ *  Reader Add
+ *  Reader Remove
+ *  Card Remove
+ * If the operation was successful then VSC_SUCCESS
+ * is returned, other wise a specific error code.
+ * */
+typedef struct VSCMsgError {
+    uint32_t   code;
+} VSCMsgError;
+
+/* VSCMsgReaderAdd          Client -> Host
+ * Host replies with allocated reader id in VSCMsgError with code==SUCCESS.
+ *
+ * name - name of the reader on client side, UTF-8 encoded. Only used
+ *  for client presentation (may be translated to the device presented to the
+ *  guest), protocol wise only reader_id is important.
+ * */
+typedef struct VSCMsgReaderAdd {
+    uint8_t    name[0];
+} VSCMsgReaderAdd;
+
+/* VSCMsgReaderRemove       Client -> Host
+ * The client's reader has been removed.
+ * */
+typedef struct VSCMsgReaderRemove {
+} VSCMsgReaderRemove;
+
+/* VSCMsgATR                Client -> Host
+ * Answer to reset. Sent for card insertion or card reset. The reset/insertion
+ * happens on the client side, they do not require any action from the host.
+ * */
+typedef struct VSCMsgATR {
+    uint8_t     atr[0];
+} VSCMsgATR;
+
+/* VSCMsgCardRemove         Client -> Host
+ * The client card has been removed.
+ * */
+typedef struct VSCMsgCardRemove {
+} VSCMsgCardRemove;
+
+/* VSCMsgAPDU               Client <-> Host
+ * Main reason of existance. Transfer a single APDU in either direction.
+ * */
+typedef struct VSCMsgAPDU {
+    uint8_t    data[0];
+} VSCMsgAPDU;
+
+/* VSCMsgFlush               Host -> Client
+ * Request client to send a FlushComplete message when it is done
+ * servicing all outstanding APDUs
+ * */
+typedef struct VSCMsgFlush {
+} VSCMsgFlush;
+
+/* VSCMsgFlush               Client -> Host
+ * Client response to Flush after all APDUs have been processed and
+ * responses sent.
+ * */
+typedef struct VSCMsgFlushComplete {
+} VSCMsgFlushComplete;
+
+#endif /* VSCARD_COMMON_H */
+
